Variable-stroke combustion engine



Sept. 1 7, 1929.

ALL. RIGHTENOUR VARIABLE STROKECOMBUSTION ENGINE Filed May 26 1927 4Sheets-Sheet l P 1929. A. RIGHTENOUR 1,728,363

VARIA BITE v STROKE COMBUSTI 0N ENGINE Sept. 17, 1929. A. L. RIGHTENOUR1,723,363

VARIABLE STROKE COMBUSTION ENGINE Filed May 26. 1927 4 Sheets-Sheet 3POWER STROKE (innu. can cofirnzssnou scnvzuema SUCTION Sept. 17, 1929.A. 1.. RIGHTENOUR VARIABLE STROKE COMBUSTION ENGINE Filed ma z's'. 19274 Sheets-Sheet 4 Patented Sept; 17, 1929 UNITED STATES PATIENT OFFICE L.RIGHTENOUR, CLIFTON H. ,FRIZELLE, A. J. sxarr, o. E. MCABTHUR, FRANK I.QUEEN, AND 0. 1). LA Fon'rAINE, ALL OF CHICAGO, ILLINOIS, AS 'rnus'mnsVARIABLE-STROKE coMBUs'rroN ENGINE Application filed May 26, i927.-Serial No. 194,455.

This invention relates to a variable stroke combustion engine, andparticularly 'to a con,- struction wherein the piston is directlyassociated with an actuating cam formed to vary 5 the length of itsstroke for the successive cycles of engine operation during a completerotation of a driven shaft. I f

In thistype of engine it is important to provide for the maximum lengthof piston stroke during the exhaust or scavenging movement and theopposite suction or intake travel which involve a one-half revolution ofthe cam while the minimum length of the piston stroke occurs duringthecompression and firing cycles when the piston is at its usual lengthof stroke. To effect such operation the piston is yieldingly held incontact with a figure 8 cam on the driven shaft and to secure the mosteificient action of the piston dur- 0' ing the successive cyclesofengine operation the movements of the piston are difierently timed sothat I obtain a variation in the length of piston stroke and also varythe time of opposite movements comprising such strokes. This may bereadily accomplished by I forming the opposite cam heads of differenttransverse width and also by offsetting. oneof the side contact faces ofthe cam ata greater distance from'the longitudinal center of the camthan its opposite face. The result is to provide actuating faces atopposite sides of each end of the cam having different arcs of curvaturewhich control the movement of the piston relative to the travel of a'given point ofthecam- I I Under this arrangement, when thepiston is atits inward limit of movement after the when the stroke is completed,while the return movem ent' of this stroke comprises the firing orpowercycle and is. more rapid than the compression travel which resultsin the greatest lev erage atthe beginning of the stroke and a reductionthereof until the piston is nearest the axis of the cam at'thecompletion of the :tourfcycles of operation.

The result'ofthe side variations of the cam face or different arcs ofcurvature thereof, is that for a fixed distance of circular travel ofagiven point on the camthe piston has imparted thereto a different extentof movement during the successive cycles of operation resultingin a muchmore efficient action than would beproduced were the side faces of thecam equal in curvature and the heads of thesame transverse diameter.

In an engi assemblage cost of repair.

ne ofthis character it is desirable to avoid extended connections suchaspiston rods between the piston and its controlling cam and I' haveprovided for the direct engagement of the piston with the cam whereby apositive action is secured; the engine parts reduced in number andclosely nested to efl'ect a material reduction in weight and cost ofconstruction; and providing a simplicity of 'constructionwhich permitsquick and reduces to a minimum the Toward this end of direct contact ofthe piston with the cam; the skirt of the piston is provided with aroller traversing the actuating faceof thecam during its rotationfandrestoring springs are extended from'thepiston skirt to'a point on the icasing below the cam; whichiprovides for a yielding con tact between thepiston and cam.

In order to guide the piston in its movementbeyond the cylinder flangesare provided at the open end thereof having curved faces conforming tothe curvature'of the cylinder which insures a full downward stroke ofthepiston in following the curvature of the cam without liability to"side wobbling movement while the relation of these guides is such thatthe size and weight of the engine tion of the wmay be reduced by theclosely nested relapiston and cam with their associated springs andguide.

In assemb ling an engine of the type before Fig'ureQ,

springswithin said chamber for retainingtlie piston and cam in yieldingcontact.

The invention has for an object to providea novel and improvedconstruction of variable stroke engine including a cylinder and pistontherein, a cooperating shaft having a controlling cam thereon for thepiston stroke and formed with heads at different distances from theshaft to' vary the length of stroke andwith" means tovary the timing ofthe pieton travel during the successive cycles inci dent-to a completerevolution of said'cam during the engine operationi A further. object ofthe invention is to provide'an improved construction =of controllingcam. having its opposite heads extended at different distances from theaxis of. the cam',-said headsbeing of different transverse diameters"and having contact faces of variable arcs to effect a difierent timingmotion of the piston during its travel upon opposite faces of eitherheadof the cam.-

Another object of the invention is to provide an improved constructionwherein the piston directly engages a controlling cam -an'd1isyieldingly held in contact therewith .soas to'securea direct actionof'one member upon theother and a closely" nested assembljageoftheparts.

1 A still further object of the invention is to-provide an improved"construction of engine casing having in its body acam chamber andacylinder atits upper portion communicating with said chambertogether-with in- "leta'nd exhaustjports at the head of said cylinder,a; piston therein, and a cam within the chamber ofthe casing adapted-todirectly engage said piston.

Other and further objects and advantages of; the invention willb'ehereinafter set forth and thenovel features thereof defined by theappended claims. r

,In:the accompanying drawings:

Figure 1- is a vertical section with parts in elevation IS a similarview taken'at a right angle toFigurelg Y e i Figure 3 is a diagramillustrating the relative cam and piston movements;

'Figure 4 isa section on the line 44 of 'F1gure'2;"- Y

Figure 6 is a detailsection of the piston. .L1ke-"reference numeralsdesignate correcasing and communicating with the cam chamber is acylinder 23 provided if desired with radiator ribs 24 while the head 25of this cylinder is fomed with the usual intake passage 26 and valve 27controlling the same and with the exhaust passage 28 and valve 29therefor. The exhaust passage communicates with a suitable discharge 30while the inlet passage 26 may be in communication with a carbureterasshown at 31 in Figure 2.

One side or head 32 of the casing 20 is provided with outwardlyradiating ribs 33 supporting a bearing 34 for the driven shaft 35. Atthe opposite side of the casing a removable head 36 is secured theretoin any preferred manner and formed with radiating ribs 37 supporting thebearing 33 for the shaft. Secured upon this shaft is the usual fly wheel39 having means indicated at 40 for connection with a starting crank orlever.

Within the cylinder 23 apiston 41 is disposed and may be either solid ortubular as shown. The lower end of this piston is formed with a skirtportion 42 providing bearings for the journal 43 of a friction roller 44which is flanged at 45 and rides upon the periphery or actuating face ofthe cam 21.

This cam comprises opposite head portions forming a large cam 46 and asmall cam 47,

'the former being provided with an apertured portion 49 inits web toproperly balance the greater size'of the portion 46. The actuating L el0 e ar 'er cam is c1 30sec a a fac 8 fthl ls lt greater distance fromthe shaft 35 than the similar face of the smaller cam 47.

The oppositeends of this cam' member are not only of greater length butalso differ in thelr transverse wldth or diameter so as to provide sidefaces which m'a-y be located at different distances from a longitudinalcentral line extending through the axis of the cam which results inproviding actuating faces at the sides ofthe cam differing in their areof curvature. r

Referring to Figures 2 and 3 it will be noted that on the larger ca-mhead 46 the actuating face 50 at one side is at different distance fromthe central line 53 of the-cam and of a diflerent curvature from theopposite actuatingface 51 while the face 48 connecting these portions isof a curvature which effects the least movement of the pistonJ At theopposite or smaller cam head47 the 'face 52 1s at the greater distancefrom the central line 53 while thezface 5 1 is of less curvature andconsequently nearer said line.

In order to insure a yielding contact between the piston roller andthe'cam I have provided spring members which in order to secure areduction in size and close nesting of the parts,are disposed atopposite sides of are. secured to the skirt by means of pins 57extending through apertures 1n the arms to prevent rocking movementthereof and the clamping screws 58 extending through the arms into thepiston skirt 42. The lower ends of these springs may be secured in anydesired manner, for instanceby means of hooked lugs 59 bolted to thecasing at 60. This novel'form of casing is also adapted to cooperatewith the valve actuating members and for that purpose an intake cam" 61is keyed to the shaft and operates upon a pusher 62 disposed in atubular portion 63 of the casing and carries the rod 64- extended to thevalve operating lever'65. I t i The exhaust cam 66 at'the opposite sideof the casing is provided with a similar construction of parts foractuating the rocker lever for the exhaust valve 29. The casing isfurther providedwith an extension 67 at one side adapted to receivethedriving gear 68 for a generator or magneto disposed upon the platform 69carried by the casing. This driving gear 68 is connected by the chain'70 with a sprocket gear 71 keyed to the shaft 35. l i

In the movement of the piston away froin its head while traversing thecurvature of the controlling cam, it is' essential to provide suitableguide means to prevent side movement of the piston and this iseffectually done by means of theparallel ribs 72 extended inward fromopposite points on the casing, these ribs being formed with guideflanges 73 having suitable curved faces 74 whichforin a continuation ofthe cylinder walls atopposite points which permits a movement of thepiston at all times in direct contact with the cam.

The general operation of theengine will be apparent from the foregoingdescription from which it will be seen that the larger-cam imparts tothe piston its greatest length of stroke during the scavenging andsuction cycles while the smaller cam head reduces the length of suchstroke for and firing cycles.

As illustrating the variation of the timing in the piston movement,reference made to the diagram of Figure 3 from which it will be seenthat the cam in its full line position the compression at the point 13.

'isfat the end of the firing stroke and about to begin the scavengingcycle. I In order to 1 illustrate the movement of agiven point on thecamsuch as *thearrow atthe left, the cam has been surrounded; a circlehaving a series of equal divisions indicated by thenumorals 1 to16inclusive, and it will be seen that the movement of the arrow from theposition 1 to 2 causes a rapid inward movement of the piston equivalentto the space between;

1 and 2 indicated atthe upper portion ofthe diagram on the wall ofthecylinder. This continues until the arrow reaches the point 3wh'en theportion of the cam ofless curvature is reached and t the speed of the:piston movement reduced so tliat ittravels a less distance inthecylinderbetween the points Sand 4 while when itreaches the point 5 ofthe circle it is atits greatest length of stroke and accomplishes acompletescavenging action'of the cylinder.

The return or suction stroke begins in the 7 travel of the arrow'fromthe point 5'to the point 6, resulting in arelativelyslow move ment asindicated on't-heupper portion ofthe diagram and the wall 51 of thelarger cam head bein got less curvature causes a rapid increase in thismovement between the points 6 and 7, and 7 and 8, while at the point 9the piston has reached the inmost limit'of its suction stroke,asindicated by dotted lines in Figure The movement from this time occursat the smaller head and the face 52 thereof effects a gradual risingmovement of t travel between the points 10,11 andt12 while thelimit ofthe short piston stroke is reached The return or firing action nowoccursand there is a slow startingmovement in the travelbetweenpoints'13'and'14 which ism teriallyincreaseddue to the, curvature of theface 54 so as to secure arapidsmovement during the firing stroke and themaximum, le- 1 verage up tothe point 16 after which the s pistoncomes toits inmost-point of travel at thepoint 1 and has completed the fourcycles ofthe engine operation with proper provision ineach cycle for avariationin the speed of the piston so as to secure the most efiiciency.

incident to the dilferencegin curvature betweenthe opposite side'facesof each ofthe cam heads. 1 p n *It will be seen that'thisassembla'ge'providesfor adirectaction of the piston upon V the camand the control ofits movement thereby while the parts are so assembledas to greatlyreduce the weight and simplify the construction of theengine so that it can be quickly assembled and reassembled and comprisesan operatingunit by which the core lated parts operate in unison toeffect the intake and GXlliLllSlJ-flOl'Il the c'ylinder'and theactiontherefrom through the cam to the drive shaft. i i i While thedetail construction of the several parts has been shown and described,the invention is not confined thereto as changes and alterations may bemade without departing from the spirit of the invention as defined bythe appended claims. 7

Having thus described my invention, what I claim as new and desire tosecure by Letters Patentis Y 1. In a variable stroke engine including acylinder and piston, a shaft, and a figure 8 cam disposed to actuatesaid piston and having heads of varied length to determine the stroke ofthe piston and its side faces at different curvature to control thetiming oft-he opposite movements of said piston intermediate its limitsof stroke.

2; In a variable stroke engine including a cylinder and piston, a shaft,a controlling cam upon said shaft operating in a path adjacent the openend of the cylinder, a piston disposed in said cylinder to directlyengage said cam and having a skirt extending parallel to the cam, andoppositely disposed springs extending from the skirt of said piston to afixed point.

3. In a variable stroke engine including a cylinder and piston, a shaft.a controlling cam upon said shaft, a piston disposed in said cylinder todirectly engage said cam and having a skirt at opposite sides of thecam, and oppositely disposed springs extending from the skirt of saidpiston to a fixed point in planes parallel to that of the cam.

4. In a variable stroke engine including a cylinder and piston, a shaft,a piston within the cylinderprovided with an anti-friction member, acontrolling cam upon said shaft disposed adjacent the open end of thecylinder in direct traversing contact with said member, springsupporting arms carried by the skirt of said piston and extending inopposite directions, and resilient members extending from said arms to afixed point beyond said shaft.

5. In a variable stroke engine, a casing provided with a cam chamber, ashaft extending therethrough, a variable stroke cam disposed within saidchamber, a cylinder extended from said chamber, a piston within saidcylinder having engaging contact with the actuating face of said cam atthe open end of the cylinder, a head for said cylinder pr0- videdwithinlet and exhaust valves, and actuating means upon said shaft for saidvalves.

6. In a variable stroke engine, a casing provided with a cam chamber, ashaft extending therethrough, a variable stroke cam disposed within saidchamber, a cylinder extended from said chamber, a piston within cylinderhaving engaging contact with the actuating face-of said cam, a head forsaid cylinder provided with inlet and exhaust valves, actuating meansupon said shaft for said valves, and tension means extending from theinner end of said cylinder to a point on the casing below said camchamber and at opposite sides of the cam therein.

7. In a variable stroke en ine, a casing provided with a cam chamber, ashaft extending therethrough, a variable stroke cam disposed within saidchamber, a cylinder extended from said chamber, a piston within saidcylinder having engaging contact with the actuating face of said cam, ahead for said cylinder provided with inlet and exhaust valves, actuatingmeans upon said shaft for said valves, tension means "extending from theinner end of said cylinder to a point on the casing below said camchamber and at opposite sides of the cam therein, an extension from saidchamber provided with auxiliary driving means, means upon said shaftprovided with a support, and means upon said shaft connected to actuatesaid auxiliary driving means.

S. In a variable stroke engine, a casing provided with a cam chamber, ashaft extending therethrough and carrying a variable stroke cam, acylinder projected from said chamber, a piston therein disposed todirectly engage said cam, and ribs projected inward from the casingwithin the cam chamber and having flanges forming a continuation of thewalls of said cylinder for guiding said piston in its movement outwardtherefrom.

9. In a variable stroke engine, a casing provided with a cam chamber,and a cylinder projected therefrom, a shaft extending through saidchamber and carrying a variable stroke cam, a piston within saidcylinder having direct contact with said cam at the open end of thecylinder, a head for said cylinder provided with inlet and exhaustvalves, opposite heads for said casing formed with shaft bearings andtubular passages, valve actuating cams disposed upon said shaft, andconnections therefrom extending through said passages to the inlet andexhaust valves respectively.

In testimony whereof I aflix my signature.

ASA LEE RIGHTENOUR.

